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West Nile threat from mosquitoes could be high this summer

Memorial Day marks the beginning of mosquito season - and West Nile virus worries - in El Paso County.
In Colorado, the first seasonal hatching for mosquitoes occurs early in June, coordinating well with an increase in camping across the state and other burgeoning human outdoor activities,...

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Memorial Day marks the beginning of mosquito season - and West Nile virus worries - in El Paso County.

In Colorado, the first seasonal hatching for mosquitoes occurs early in June, coordinating well with an increase in camping across the state and other burgeoning human outdoor activities, said Lee Griffen, program supervisor for the El Paso County Health Department's environmental health division.

"We start seeing an uptick in calls from the public right around Memorial Day," Griffen said. "People are outside more and starting to actually see mosquitoes."

According to the Centers for Disease Control and Prevention, 2012 saw the second-worst outbreak of West Nile virus since the mosquito-borne illness was first detected in the U.S. in 1999 in New York. Those infected with West Nile, which has no vaccine or cure, manifest flu-like symptoms within two weeks of being bitten by an infected mosquito. For most people, symptoms resolve on their own over time, but if the virus settles in the brain, the outcome can be dire. Last year, of the 5,674 cases reported in the lower 48 states, the District of Columbia and Puerto Rico, 286 people died, making last year the most deadly season for the virus on record.

Of the 131 confirmed and probable cases of West Nile documented in Colorado last year, there were five fatalities. Texas saw 89 deaths from the virus during that period, about a third of the fatalities reported nationally. During the worst outbreak here a decade ago, in 2003, Colorado led the nation in the number of cases (2,947) and fatalities (63).

"We do see patterns repeat themselves, as far as the risk, and we're probably due - our neck of the woods, Colorado and El Paso County - for a significant year for virus transmission," Griffen said. "But again, it really depends on what's going on with the weather as to how many are breeding. The weather dictates the density of mosquitoes."

A dry climate, coupled with an especially dry spring, means Colorado hosts a lower mosquito population than is found in damper regions, but the species of mosquito most commonly found here - the culex tarsalis - is known to be a leading carrier of the West Nile virus, Griffen said.

"Because of our arid conditions we don't experience the volume of mosquitoes that many states that have water do, but the mosquitoes that do hatch out are more suspect of carrying West Nile, so we do see cases," Griffen said. "We have other species that carry it (West Nile), but the culex tarsalis carries the disease very well."

The culex tarsalis tends to seek its meals in the cool hours around dawn and dusk, so Griffen encourages those who must be outdoors at those times to take precautions.

"Make sure you're wearing appropriate DEET and long sleeves and pants if you're going to be out in the morning and evening," Griffen said. Repellent should contain at least 20 percent DEET to be effective.

Avoid creating, or hanging around, areas with standing water.

"When you do water, make sure the water doesn't pool or sit around," Griffen said. "Mosquitoes love stagnant water. That means flower pots, bird baths, gutters, anything that would hold water from the sky or the hose."